1. Field of Invention
The invention relates to a method for modifying an etch rate of a material layer.
2. Description of Related Art
Typically, during fabrication of integrated circuits (ICs), semiconductor production equipment utilize a (dry) plasma etch process to remove or etch material along fine lines or within vias or contacts patterned on a semiconductor substrate. The success of the plasma etch process requires that the etch chemistry includes chemical reactants suitable for selectively etching one material while etching another material at a substantially lesser rate.
In present IC devices, exotic materials have been introduced to replace conventional materials used in semiconductor processing, thereby improving various electrical properties of the IC devices. For example, in front-end-of-line (FEOL) semiconductor processing, high dielectric constant (high-k) materials are desirable for use as transistor gate dielectrics. Preliminary high-k materials used in this role were tantalum oxide and aluminum oxide materials. Currently, hafnium-based dielectrics and possibly lanthanum-based dielectrics are expected to enter production as gate dielectrics, thereby replacing the current silicon oxide and silicon oxynitride materials. Moreover, in FEOL semiconductor processing, metal-containing materials are desirable for use as transistor gate electrodes in future generations of electronic devices. Currently, metal electrodes containing Ti, Ta, and/or Al (e.g., TiN, TaN, Al2O3, TiAl) are expected to enter production as metal electrodes, thereby fully or partly replacing the current polycrystalline gate electrode. Of course, the introduction of new materials to semiconductor processing is not limited to only FEOL operations, but is also a trend in metallization processes for back-end-of-line (BEOL) operations. Moreover, in memory devices, new and exotic materials are used and introduced.
With current materials and the advent of these new materials in electronic device processing, the ability to etch these old and new materials while maintaining the integrity of pre-existing layers and/or structures faces formidable challenges. Conventional etch processes may not achieve practical etch rates of these materials or attain an acceptable etch selectivity relative to underlying or overlying materials.